Tag Archives: IJN

The Attack on Pearl Harbor: Strategy, Combat, Myths and Deceptions (Haverton, PA/Newbury: Casemate, 2011) by Alan D. Zimm analyses the Japanese attack on Pearl Harbor on 7 December 1941 by use of operation research techniques.

Casemate, the publisher, say that the book asks:

Questions never before asked or answered on the Japanese attack from an operational and tactical perspective.
The attack on Pearl Harbor on 7 December, 1941, has been portrayed by historians as a dazzling success, “brilliantly conceived and meticulously planned”. With most historians concentrating on command errors and the story of participants’ experiences, this book presents a detailed evaluation of the Japanese attack on Pearl Harbor on an operational and tactical level.
It examines such questions as: Was the strategy underlying the attack sound? Were there flaws in planning or execution? How did Japanese military culture influence the planning? How risky was the attack? What did the Japanese expect to achieve, balanced against what they did achieve? What might have been the results if the attack had not benefited from the mistakes of the American commanders? The book also addresses the body of folklore about the attack, supporting or challenging many contentious issues such as the skill level of the Japanese aircrew, whether midget submarines torpedoed Oklahoma and Arizona, as has been recently claimed, whether the Japanese ever really considered launching a third wave attack, and what the consequences might have been.
In addition, the analysis has detected for the first time a body of deceptions that a prominent Japanese participant in the attack placed into the historical record, most likely to conceal his blunders and enhance his reputation. The centrepiece of the book is an analysis using modern Operations Research methods and computer simulations, as well as combat models developed between 1922 and 1946 at the U.S. Naval War College. The analysis puts a new light on the strategy and tactics employed by Yamamoto to open the Pacific War, and a dramatically different appraisal of the effectiveness of the attack on Pearl Harbor.

Zimm subjects the strategy behind the attack, the tactical plan and the actual attack to detailed analysis. He uses the assumptions made by the US Naval War College in its wargames and the outcome of other actions in the Pacific War to evaluate the likely outcomes of various options for both sides.

According to Zimm, Admiral Yamamoto Isoruku, commander of the Japanese Combined Fleet, wanted to sink at least one battleship as he believed that this would destroy the American will to fight. The battleships were therefore the main targets of the attack, but the carrier aviators who planned it regarded the aircraft carriers as the main threat, and allocated a significant number of aircraft against them.

The Japanese plan was inflexible. B5N Kate bombers that could carry either bombs or torpedoes were allocated to one or the other early on in the planning, and their crews were then trained for only one role, making future changes to the bomb/torpedo mix impossible.

The absence of the carriers from Pearl Harbor was known the day before, but no changes were made in the plan, resulting in a large number of torpedoes being wasted on the target ship USS Utah, an unarmed former battleship. Some authors have claimed that the Japanese mistook her for a carrier because her gun turrets had been removed, but Zimm quotes Japanese reports to show that she was attacked in the belief that she was an active battleship.

The attack was unco-ordinated. The bombs of the D3A Val dive bombers could not penetrate battleship armour. They should either have attacked the battleships in the first wave along with the torpedo bombers in order to suppress their AA fire or else bombed cruisers, which they could sink. Instead, the Vals of the second wave wasted many of their bombs on battleships that they could not sink.

The Kate level bombers, which destroyed the USS Arizona, and the attacks on airfields exceeded expectations. However, more ships would have been sunk if more Kates had carried torpedoes, and sinking cruisers was a better use of the Vals’ bombs than destroying aircraft. The Japanese aircrew were badly let down by a large number of dud bombs.

Yamamoto was willing to attack even without the benefit of surprise. Zimm convincingly shows that this would have resulted in very heavy Japanese casualties and much lower American ones.

Zimm characterises Yamamoto as a gambler, who was willing to take big risks. He included midget submarines in the attack. They achieved nothing and risked alerting the Americans. Zimm shows why the theory that a midget submarine torpedoed the Arizona is highly unlikely to be true.

The Americans ought to have had a warning system that would have given them 40 minutes’ warning. Ships would then have had their watertight doors and hatches closed and their AA guns manned, whilst the fighters would have been scrambled. Zimm therefore disagrees with those who try to exonerate General Walter Short and Admiral Husband Kimmel, the US Army and USN commanders.

The attack was a success. The target was to put at least four battleships out of action for a minimum of six months. Yamamoto wanted to destroy at least one battleship, and the Arizona and Oklahoma were lost permanently, but this did not have the psychological effect that he expected. The Nevada was out of service for over six months, and the California and West Virginia did not return to service until 1944, although this delay was partly because they were heavily modernised as well as being repaired. More US aircraft were destroyed than anticipated.

Zimm’s points are that huge risks were taken to achieve this and that a better plan could have inflicted even heavier casualties.

Zimm refutes three well known claims about the battle, which I had accepted until reading his book. The first is that the Japanese should have launched a third strike against shore facilities, including oil tanks. The Navy Yard  was too big to be seriously damaged by the force available. The oil tanks could have been destroyed, but they would have been repaired, and short-term supply shortages could have been met by a re-allocation of Allied tankers. Zimm points out that the Japanese paid little attention to logistics in their planning, so why would they consider disrupting enemy logistics?

He argues that the assertion that there was a heated discussion on whether or not to launch a third strike onboard the Japanese flagship Akagi is a fabrication of Commander Fuchida Mitsuo, the attack leader. Fuchida comes out poorly from this book. Previous research, including this paper by Jonathan Parshall, has doubted his account of the Battle of Midway and his claim to have present at the Japanese surrender in 1945.

The second claim is that it would have been better for the Japanese to meet the Americans at sea. Two of the four battleships that were sunk in the shallow waters of Pearl Harbor were subsequently raised and repaired. They would have been lost if they had suffered the same damage at sea.

Zimm points out that the Japanese would not have scored as many hits on ships that were free to manoeuvre at sea and had their AA guns fully manned. The hits would not have been as devastating on ships that had all their watertight doors and hatches closed.

Comparisons with the sinking of Force Z a couple of days later are invalid. The US ships had better AA systems than the British ones, the US force was larger and the British were attacked by more torpedo bombers than were at Pearl Harbor. At sea, the Japanese could have expected to sink only one US battleship, and then only if they had concentrated their attack on a single ship.

The final claim is that the Japanese aviators were exceptionally well trained and mostly combat veterans. In fact, two of the carriers, Shokaku and Zuikaku, were newly completed, and many of their aircrews were just out of training. Not many of the men on the other four carriers were combat veterans, as carrier aircrews had played relatively little part in the Sino-Japanese War.

The book includes an appendix in which Zimm imagines how the Japanese could have carried out a better attack. More torpedo bombers, better co-ordination and superior target selection result in higher US losses. There is no attempt to extrapolate this into a Japanese victory in the war. It is not one of the counter-factuals, popular on the internet, where one change in weapons production or tactics results in an Axis victory in the Battle of Britain/Stalingrad/Midway and thus the war.

This is an excellent military analysis. It is not a book for everyone. It is not one for anybody who does not know much about the battle or the causes of the Pacific War. It will not appeal to those who dislike acronyms, tables or lots of numbers. There are a number of extracts from memoirs, but these are intended to emphasis points in the analysis, rather than trying to show what it was like to be there.

For those who have some knowledge of the battle, but want a deeper analysis, it is highly recommended.

I read a Kindle copy. The text and quotations were clear, but I would advise e-book readers to switch to landscape format when studying the many maps and tables, which are too small to be legible in portrait format.